A variable optical attenuator (VOA) is widely applied in optical communications, and it has a main function of dynamically controlling attenuation of an optical signal and is an indispensable key component in an optical network. The variable optical attenuator is generally required to have a wide attenuation range, high precision, high stability, a small size, and a low cost. Currently, in an optical communications system, two main technologies for implementing a high-end variable optical attenuator are available: a micro electro mechanical system (MEMS) technology and a liquid crystal (LC)+optical wedge technology.
A VOA based on the MEMS technology controls an attenuation extent of light by using a tilt angle of an MEMS micro reflector, and has a small size but low shockproof performance. Due to use of a birefringent wedge, a VOA based on the LC+optical wedge technology is large in size, costly, and has a problem of being difficult to align an optical path.